This invention relates generally to a coaxial type of breathing circuit used to supply gas for inhalation by a patient and for receiving and carrying away the patient's exhalation.
Coaxial circuits for breathing circuits have been used for some time, i.e. Bain U.S. Pat. No. 3,856,051, and they include an inner tube that supplies the inhalation gas to the patient. That gas may be air with mixture of O.sub.2 in the case of a patient being breathed by a ventilator, or the inhalation gas may include a vaporized anesthetic in the case where a patient is anesthetized.
An outer tube surrounds the inner tube and is generally coaxial therewith. The outer tube is connected to the patient such that a flow path for exhaled gases is formed between the annular space between the inner and outer tubes. The outer tube is generally corrugated for flexibility.
One difficulty with the coaxial circuit, particularly in anesthesia breathing circuits, is the assurance of the integrity of the inhalation circuit. Since the inner tube carries fresh gas to the patient or, in the case of an anesthesia circuit, the anesthetic with fresh gas, it is extremely important for the attending personnel to be immediately aware of an inadvertent disconnection.
At the machine end, a disconnection of the inner tube can escape immediate attention, since its view is shielded by the surrounding corrugated outer tube. Thus, it is possible for the inner tube to be disconnected, yet the overall coaxial circuit has the appearance of being completely intact. The potentially dangerous situation of rebreathing exhaled gases is created, which can result in hypoxia and CO.sub.2 buildup in the patient.